Process for producing ethanol from corn dry milling

1. A process for the production of an ester of acetic acid, comprising:

a. conducting a yeast fermentation in a corn preparation to produce ethanol;

b. distilling the ethanol from the yeast fermentation to produce a bottoms fraction;

c. hydrolyzing the bottoms fraction;

d. separating the hydrolyzed bottoms fraction into a solids fraction and a liquid hydrolyzate;

e. culturing a homofermentative microorganism in the liquid hydrolyzate to produce acetate, acetic acid or mixtures thereof; and

f. chemically convening the acetate, acetic acid or mixtures thereof to an ester of acetic acid.

2. The process, as claimed in claim 1 , wherein the step of hydrolyzing comprises hot water pretreatment of the bottoms fraction.

3. The process, as claimed in claim 1 , wherein the step of hydrolyzing comprises enzymatic hydrolysis.

4. The process, as claimed in claim 1 , wherein the step of hydrolyzing comprises contacting the bottoms fraction with xylanase and cellulase enzymes.

5. The process, as claimed in claim 1 , wherein the solids fraction comprises a majority of protein from the corn.

6. The process, as claimed in claim 1 , wherein the solids fraction comprises at least about 35% protein on a dry weight basis.

7. The process, as claimed in claim 1 , wherein the solids fraction comprises the lipid fraction from the corn.

8. The process, as claimed in claim 1 , wherein the volume of the solids fraction is about one-half the volume of distiller's dried grains and solubles (DDGS) produced by the same volume of corn preparation.

9. The process, as claimed in claim 1 , further comprising the step of drying the solids fraction.

10. The process, as claimed in claim 9 , wherein the step of drying is conducted with a dryer suitable for producing DDGS from a bottoms fraction.

11. The process, as claimed in claim 9 , wherein the step of drying is conducted without a pre-step of separating and concentrating a liquid portion of the solids fraction.

12. The process, as claimed in claim 1 , wherein the fermentable fraction of the liquid hydrolysate is less than about 6% by weight.

13. The process, as claimed in claim 1 , wherein at least about 70% of carbon in the bottoms fraction is converted into ethanol.

14. The process, as claimed in claim 1 , wherein the homofermentative microorganism is a homoacetogenic microorganism.

15. The process, as claimed in claim 14 , wherein the homoacetogenic microorganism is of the species Clostridium thermoaceticum or Clostridium formicoaceticum.

16. The process, as claimed in claim 1 , wherein said step of culturing comprises:

(i) converting by fermentation the liquid hydrolyzate into lactic acid, lactate or mixtures thereof; and

(ii) converting by fermentation lactic acid, lactate or mixtures thereof into acetic acid, acetate or mixtures thereof.

17. The process, as claimed in claim 16 , wherein said step (i) comprises a homolactic fermentation.

18. The process, as claimed in claim 17 , wherein said homolactic fermentation is accomplished by a microorganism of the genus Lactobacillus.

19. The process, as claimed in claim 16 , wherein said step (ii) comprises a homoacetic fermentation.

20. The process, as claimed in claim 19 , wherein said homoacetic fermentation is accomplished by a microorganism of the genus Clostridium.

21. The process, as claimed in claim 1 , wherein step (f) comprises:

(i) esterifying said acetic acid to an acetic acid ester in the presence of an alcohol; and

(ii) hydrogenating said acetic acid ester to said ethanol and said alcohol.

22. The process, as claimed in claim 21 , wherein said alcohol produced in step (ii) is recycled to said step (i).

23. The process, as claimed in claim 21 , wherein said alcohol in step (i) comprises ethanol produced by the yeast fermentation of step (a).

24. The process, as claimed in claim 1 , further comprising:

a. acidifying said acetate with carbon dioxide to produce acetic acid and calcium carbonate;

b. esterifying said acetic acid with an alcohol to form an ester; and

c. recovering said ester.

25. The process, as claimed in claim 24 , wherein said ester is recovered by distillation.

26. The process, as claimed in claim 25 , wherein said distillation is a reactive distillation capable of pushing the acidification and esterification equilibria to high conversion to the desired ester product.

27. The process, as claimed in claim 24 , wherein said ester is converted to ethanol.

28. The process, as claimed in claim 1 , wherein said ester of acetic acid is ethyl acetate.

29. The process, as claimed in claim 1 , further comprising contacting the bottoms fraction with a protease.

30. A process for upgrading the unfermented fraction of corn from a yeast fermentation based corn dry milling ethanol process, comprising:

a. hydrolyzing a bottoms fraction produced by distilling ethanol from the yeast fermentation;

b. separating the hydrolyzed bottoms fraction into a solids fraction and a liquid hydrolyzate;

c. culturing a homofermentative microorganism in the liquid hydrolyzate to produce acetate, acetic acid or mixtures thereof; and

d. chemically converting the acetate, acetic acid or mixtures thereof to a product selected from the group consisting of ethanol and ethyl acetate.

31. A process for the production of an ester of acetic acid, comprising:

a. culturing a homofermentative microorganism in a liquid hydrolysate to produce acetate, acetic acid or mixtures thereof, wherein the liquid hydrolysate is a liquid fraction of a hydrolysate of a bottoms fraction resulting from distilling ethanol from a yeast fermentation; and

b. chemically convening the acetate, acetic acid or mixtures thereof to an ester of acetic acid.